Some automotive drive axles include an axle housing supporting a differential assembly in an internal cavity. The differential assembly includes a gearset which is supported within a differential housing to facilitate relative rotation between a pair of output shafts. The gearset may include a pair of helical side gears that are splined to the ends of axle shafts. The helical side gears are meshed with helical pinions rotatably supported on a cross pin coupled to the differential housing. As an alternative, paired sets of meshed pinions rotatably supported in bores formed in the housing can be meshed with the side gears to define a parallel axis differential. In response to speed differentiation between the output shafts, torque transmitted through meshed engagement of the side gears and pinions generates thrust forces that are exerted by the gear components against the wall surface of the differential housing to frictionally limit the speed differentiation and proportionally deliver torque between the output shafts.
In addition, automotive drive axles typically include a hypoid gearset for changing the direction of power transmission from an axis parallel to the direction of vehicle travel to an axis perpendicular thereto. The hypoid gearset includes a ring gear coupled to the differential housing and a pinion gear journally supported within the axle housing. To facilitate proper function of the drive axle, the differential housing is mounted on a pair of differential bearings.
In some drive axles, the pinion gear is supported by a bearing assembly in a pinion housing or unit. The pinion unit may define a cylindrical body portion and an outer flange portion. The outer flange of the pinion unit is adapted to be secured to the axle housing in an installed position. Typically, the transition between the cylindrical body and the flange portion of the pinion unit comprises an undercut region formed by a machining process necessary for economical manufacturing. In some instances, the undercut region may influence additional stress on the pinion unit during operation causing premature failure.
In a conventional axle housing incorporating a pinion unit, the axle housing is formed by a casting process such as sand casting. After the axle housing is cast, a secondary operation is needed to form an oil feed path in the axle housing. The oil feed path communicates oil from a cavity of the axle housing toward the bearing assembly in the pinion unit.